Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Why is galvanized pipe not used in hydronic systems?

Chris_82 Member Posts: 321
It was used in great quantities in the Prudental Building in Boston, as well as in the sanitary piping. It was removed 20 years later at great cost. It was another "new" product that the engeneers were raving about! Unfourtuantly no one mentioned it does rust. Water over time and it's not called the universal solvent for nothing! On the other hand pure tin piping was installed at Sloan Kettiring up town 40 years ago when the first hospital needed it for their pure water system. The only current problem is the carpenters, laborers and others keep removing the stuff because of its current scrap value.


  • Dave Janquart
    Dave Janquart Member Posts: 2

  • Brad White_9
    Brad White_9 Member Posts: 2,440

    is reactive with too many metals, electrolytically and chemically. When zinc oxide is created it forms a powdery precipitate which settles in inconvenient places such as control valve seats. Galvanized pipe is banned (at least in MA) for gas piping for similar reasons; it reacts poorly with high concentrations of ethyl mercaptan, the odor agent.

    If zinc were a pre-schooler and a hydronic system were a day-care center, the term "does not play well with others" comes to mind.

  • Chris,

    galvanized a "new" product?? It has been around a long, long time. Never heard water referred to as "universal solvent" either, just out of "curiosity" how long have you been in the trade?
    Anyway,,I`m with Brad on the zinc issue.

  • hr
    hr Member Posts: 6,106
    It's not needed :)

    the galvanized coating is to prevent rust and corrosion. In a closed loop, O2 free hydsronic system steel and iron components work fine and a less expensive and more readily available.

    I see no reason galvanzed pipe and fittings could not be used. Again with no O2 present electrolsis would not occur.

    I've seen a handful of old Chiles Power Systems solar/ wood boiler fired hydronic systems piped with galvie over 20 years ago.

    Glycol providers caution against zinc in contact with hydronic inhibited glycols, however.

    hot rod

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • bobbyg_2
    bobbyg_2 Member Posts: 139

    I remember seeing the term first "universal solvent" in a chemistry textbook. I have said it often. I also think when he said "new" galv. he meant "new" to that time period, but he didn't say when that time period was.

    I'ven been in the industry approx. 8 years.......
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Be ESPECIALLY wary of adding galvanized to an existing black pipe system--it will scale up with amazing speed--at least with hard, alkaline water that for some reason doesn't seem to faze black pipe.
  • hr
    hr Member Posts: 6,106
    NFPA-54 allows galvanized for gas and LP?

    I just took my State LP recertification last week and this question came up. I understood it was the sulpher content of the fuel, not the odorant?

    Our instructor, a former LP installer told us galvanized was required and prefered in many areas deep south for under ground LP. Plastic has since taken over that market.

    hot rod

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Water as \"Universal Solvent\"

    Chemistry book and chemistry teacher...

    Here's the result of a Google search for Universal Solvent

    To paraphrase what I remember from my first-year chemistry teacher, "Water is the universal solvent because it can dissolve more substances than anything else."

    I also seem to remember that "oil" is the major exception and that water and oil are so distasteful of one another that the only way they can combine is via colloidal suspension where both oil and water both combine with another substance (often "air") yet retain their individual properties. Think mayonnaise.

    Water is so ubiquitous (existing or being everywhere at the same time) that we very often forget how amazing it really is...
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Source unknown: "I used to believe that most old house problems were caused by water. I've learned that all old house problems begin with water."

    No other substance occurs in three states (vapor, liquid, solid) as can be identified by our senses. The so-called fourth state (plasma) [probably] occurs in our experience whenever hydrogen combines with oxygen--but we can only identify such indirectly...say in a radiant burner...
  • Brad White
    Brad White Member Posts: 2,398
    Galvanized and Gas

    Hot Rod,

    Natural gas has no real sulphur content, occasional traces of dihydrogen sulfide and other things in trace components among the principal methane, ethane, etc. Not enough to be of concern and too inconsistent I would think.

    The ethyl mercaptan (C2H6S) has sulphur in it. It may well be the sulphur in it that is the issue. As mentioned at Viessmann, they had issues with their copper internal gas lines in a couple of Colorado counties due to higher mercaptan concentrations. So even on copper the stuff is corrosive.

    The use of galvanized for underground is probably for reasons of external corrosion, not sure you can get it externally dipped only. (When hot dipping any hollow member you have to have a vent; not sure how to cap and dip a pipe with that in mind yet keep the molten zinc out.)

    NFPA-54 apparently does allow galvanized but Massachusetts Code does not. MA used to quote NFPA-54 verbatim in practical entirety but now due to copyright infringement, they incorporate it as a reference standard. On top of this, there is a chapter in our gas code on Massachusetts Modifications to NFPA-54 and it is in there that the galvanized pipe is outlawed.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • BAB
    BAB Member Posts: 118
    galvanized vs plated

    The field term of "galvanized" is actually very general. A lot of "galvanized" items are actually zinc or cadnium (older fittings) plated. Most people can not tell the difference between zinc plated vs hot dipped zinc galvanized. Galvanized is a thicker coating, is usually inconsistant in thickness, sometimes has drip marks, crude looking and can not coat some objects.

    The field rules for not using galvanized apply also to zinc plated pipe/fittings. Bromley
  • Bob D._2
    Bob D._2 Member Posts: 34
    Galvanized & Glycol, Un-good

    One other aspect of the "doesn't play well with others" concept is that when a glycol solution is used in a galvanized pipe hydronic system, you get a very cool, thick (about the consistency of Karo, or thin mortar), gray-black gunk (precip.) that pretty much shuts you down. You can flush and fill to your heart's content, but it just keeps coming back. Not that I've ever had it happen on one of my projects . . . . . .
  • Kevin Pulver
    Kevin Pulver Member Posts: 67

    Chris is right about water being referred to as "the universal solvent" because it will dissolve more stuff than anything else. I remember arguing with my high school science teacher (none of you can imagine that can you) asking him if maybe gasoline wouldn't dissolve more stuff. Nope, he said, water is it. I am with you though wondering what Chris meant about the time frame of the galvanized.
    I want to thank Brad for the very interesting trivia about the sulfer content coming from the "stink additive". I was like hot rod and thought it was part of the gas itself.
    Trivia like that really helps me to remember stuff better.
    Thanks to all you guys who share your knowledge. I appreciate that more than I did in high school! Kevin
This discussion has been closed.